An OLED (Organic Light Emitting Diode) display element is a device in which organic semiconductor films are activated to emit light by a current. The OLED display element has a sandwich structure, and generally comprises an anode, a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer and a cathode. Under the effect of an external electric field, electrons and holes are respectively injected into the organic light emitting layer, and recombine in the light emitting layer to form excitons which radiate to emit light. The OLED display element has advantages like large contrast, high brightness, self-emitting, wide color gamut, light in weight and thin in profile, so that it has been considered as a promising generation of display technique.
An AMOLED (Active Matrix Organic Light Emitting Diode) display element is a kind of the OLED display element. As for a R/G/B type AMOLED display element, an AMOLED display element is a pixel unit comprising R/G/B sub-pixels. R/G/B sub-pixels of the AMOLED display element are formed by FMM (Fine Metal Shadow Mask) technology.